/*标签初始化*/
*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}
body{
    background: darkolivegreen;
}
.container{
    width: 1200px;
    margin: auto;
}
.container::after{
    display: table;
    clear: both;
    content: "";
}
.col4{
    float: left;
    width: 33.333333%;
    background: deeppink;
    height: 100px;
}
@media (max-width:600px) {
    .container{
        width: 100%;
    }
    .col4{
        width: 100%;
    }
}